Ion generator and method



Feb. 21, 1961 w. w. HICKS ETA]. 2,972,680

ION GENERATOR AND METHOD Filed April 26, 1956 IS 'F'lE *25 cm! lew INVENTORS VV/Y/iam W Hick; y John C [Becks/7" ION GENERATOR AND METHOD William Wesley Hicks, San Francisco, and John Collier Beckett, Kentfield, Calif., assignors to Ionaire, Inc., San Francisco, Calif., a corporation of California Filed Apr. 26, 1956, Ser. No. 580,902

4 Claims. (Cl. 250-44) This invention relates generally to a method and apparatus for generating ions and more particularly to a method and apparatus for generating ions with soft beta radiation and discharging ions of the desired polarity into a body of air.

Certain ion generators such as those of the type disclosed in Patent No. 2,594,777 have been found to be relatively expensive to operate because the radioactive sources utilized therein are very expensive and have a relatively short half life.

In general, it is an object of the present invention to provide an improved method and apparatus for generating ions in which soft beta radiation is utilized.

Another object of the invention is to provide apparatus of the above character in which the radioactive source is tritium.

Another object of the invention is to provide apparatus of the above character in which the radioactive source serves as an electrode for the collection of undesired ions.

Other objects and advantages of the present invention will appear from the following description taken in conjunction with the accompanying drawing in which:

Figure 1 is a view partly in cross section of apparatus incorporating the present invention.

Figure 2 is a view schematically illustrating a portion of the device together with the electrical circuit connections.

Figure 3 is an enlarged cross sectional view of a portion of the apparatus showing the electrostatic field.

In accordance with the present invention, we employ a radioactive source which emits soft beta particles. The soft beta particles serve to ionize the air in a limited zone adjacent the radioactive source. The radioactive source is mounted in an air stream and serves as an electrode. An additional electrode is mounted in the air stream and carries a charge of one polarity or sign. The radioactive source carries a charge of opposite polarity or sign to create an electrostatic field between the radioactive source and the additional electrode. The electrostatic field serves to separate the ions as they are created. The ions of the sign opposite that of the sign of the charge placed on the radioactive source are collected by the source and ions of the same sign as that of the charge on the radioactive source are repulsed from the source and follow the electrostatic flux lines towards the additional electrode and pass into the airstream which sweeps them past the additional electrode and into the surrounding body of air. The radioactive source may be shielded from the moving airstream to facilitate separation of the ions.

In the embodiment of our invention illustrated in the drawing, we have provided suitable means such as a duct or tubular member 11 for carrying an airstream. Suitable means is also provided for forcing air through the duct 11 and can consist of a housing 12 having an outlet 13 connected to the lower end of the duct. Mounted within the housingis a blower 14 which is driven by a Patented Feb. 21, 1961 motor 16. The blower serves to draw air through a screened inlet 17 and discharges the same through outlet 13 and into the duct 11. A handle 18 is mounted on the housing and serves as an enclosure for a rectifier 19 and a. transformer 21.

A radioactive source 23 which emits soft beta particles is mounted in the lower portion of the duct 11. One radioactive source found to be suitable for this purpose is tritium foil 24 which is manufactured by US. Radium Corporation of New York, New York, by a process in which a metal such as zirconium is caused to absorb tritium gas. The tritium foil may be in the form of a disc in a plane perpendicular to the axis of the duct 11 or it can be in the form of a cylinder parallel to the axis of the duct. As shown in the drawing, the tritium foil 24 may be bonded to the upper surface of a disc 26 of suitable metal such as nickel. The nickel disc 26 serves to prevent radiation from the lower surface of the foil.

Foil 24 and disc 26 are supported within the duct 11 by suitable means such as the circular plate 27 which is provided with clips 28 that are adapted to frictionally engage the peripheral edge of the foil 24 and the disc 26 to hold them in a desired position. Plate 27 is supported by a conducting rod 29 which is mounted in a hemispherical member 31 of suitable insulating material. Disc 26 is recessed within a cavity 32 in the upper portion of member 31 for a purpose hereinafter described. A banana plug 33 is mounted on the lower end of rod 29 and is adapted to be mounted in sleeve 34. Sleeve 34 is carried by an insulating block 36 which is suspended within the duct 11 by suitable means such as between straps 37 and 38. Strap 37 is fastened to the side wall of the duct whereas strap 38 is fastened to strap 37 and clamps insulating block 36 between the two straps. The lower portion of sleeve 34 is provided with a flange 39 which is insulated from straps 37 and 38 by a washer 41 of insulating material. Sleeve 34 is electrically connected to the rectifier 19 by a conductor 42 as hereinafter described. It is apparent that since conductor 42 is electrically connected to the tritium foil 24 the tritium foil will serve as one electrode.

Suitable additional electrode means 43 is mounted downstream from the radioactive source 23 and can consist of a vertical rod-like electrode 44. The rod-like electrode 44 is supported by suitable means such as a pair of tubular members 46 of insulating material. The tubular members 46 are also insulated from the duct 11 by insulating washers 47. A conductor 48 extends through one of the tubular members 46 and is connected to the rod-like electrode 44 by suitable means such as solder. The other end of the conductor is connected to the rectifier 19 as hereinafter described.

The circuit diagram shown in Figure 2 includes current supply lines L1 and L2 which may be standard volt 60 cycle A.C. Conductor 51 connects line L1 to one side of motor 16 and the other side of the motor 16 is connected to line L2 by conductor 52. Conductor 52 is connected to ground. One side of the primary winding of transformer 21 is connected to conductor 51 and the other side is connected to conductor 52. One side of one pair of opposite junctions of rectifier 19 is connected to one side of the secondary winding of transformer 21 by conductor 53 and the other side of the same pair of the opposite junctions is connected to the other side of the secondary winding by conductor 54. The negative terminal of the other pair of opposite junctions of rectifier 19 is connected to the tritium foil 24 by conductor 42 as hereinbefore described. The positive terminal of the same pair of opposite junctions is connected to the rod electrode 44 by conductor 48 as hereinbefor described. 7

Operation of our ion generator may now be briefly described as follows: 'Let it be assumed that current is being supplied to lines L1 and L2 to the transformer 21 and the rectifier 19. This causes a charge of one sign or polarityto be applied to the electrode'24-of radioactive material and a charge of the opposite sign or polarity to be applied to the additional electrode 44. As shown in Figure 4, a positive charge is applied to electrode 24 and a negative charge to electrode 44. However, if desired, the polarities may be reversed.

When charges of opposite polarity are placed on the rod-like electrode 44 and the electrode 24 of radioactive material, an electrostatic field is created between them similar to that shown in Figure 3. the electrostatic flux lines terminates on the electrode 24 and the other end terminates on the electrode-44. The electrode of tritium foil 24 continuously emits a plurality of soft beta particles which causes ionization of the air immediately adjacent the upper surface of the tritium foil. With the use of tritium foil having a beta radiation of .0189 mev. it has been found that most of the ionization occurs within of the upper surface of the foil. As soon as the positive and negative ions are formed by ionization of the air, they are separated by the electrostatic field which is present at the upper surface of the foil. Ions having a sign opposite the sign of the electrode 24 are collected by the electrode 24 and ions of the same sign are repulsed by electrode 24 and follow the electrostatic flux lines towards the additional electrode 44. As soon as the ions are repulsed by electrode 24 towards the additional electrode 44, they pass into the airstream in duct 11 and are carried by the airstream past the additional. electrode and into the surrounding air. The additional electrode 44 should be spaced a distance from the foil electrode 24 at least 2 /2 times the distance traveled by soft beta particles in air to prevent collection of the desired ions before they can be swept away.

It has been found that the most efiicient ion separation can be effected in relatively quiet air and therefore the tritium foil 24 is shielded from the airstream by the hemispherical member 31. As is apparent from Figure 1, the airstream is deflected outwardly toward the side wall of the duct or tubular member 11 by hemispherical member 31. Since the tritium foil is recessed within the hemispherical member, it is adequately shielded from the airstream. The airstream moves inwardly towards the .center of the duct after it has passed member 31 and thus passes through the electrostatic field between the electrodes 24 and 44 to carry the ions of the desired sign out of the tubular member 11. The ions of the undesired sign are collected by the foil electrode 24 before they can be blown out of the tubular member.

Since the ionization occurs in a region or zone immediately adjacent the tritium foil, recombination of the ions will occur unless they are immediately separated. Therefore, it is generally desirable to use relatively high voltages to cause a rapid separation of the ions. However, the voltage should not be so high as to produce ozone or nitrous oxide.

By way of example, one ion generator which gives very excellent results has the following dimensions, voltages and air velocity. The tritium foil 24 is approximately 1" in diameter and is separated from electrode 44 by approximately 2". The diameter of the duct 11 is not critical and is grounded to prevent shock. Electrode 44 is operated at a positive 300 volts and electrode 24 is operated at a negative 300 volts. An air velocity of 400 feet per minute is used with these voltages; However, it has been found that satisfactory results can still be obtained when the potential difference between electrodes 24 and 44 is between 300 volts and 1200 volts and when the air velocity is between 200 and 1500 feet per minute. In general, it has been found that the higher the voltage 'difierence between the electrodes, the higher the airstream One end of each of ticularly suitable for the production of light and intermediateionsr By light ions or small ions, we mean those ions having mobilities between 1.0 and 2.0 centimeters per second for a field of one 'volt per centimeter. By intermediate ions we mean those ions having mobilities between 0.01 and 0.1 centimeter per second for a field of one volt per centimeter. The ions produced by our apparatus are mostly light'ions. The intermediate ions formed depend greatly upon the amount of contaminants in the airstream.

Our device has only been described in conjunction with the use of soft beta radiation. By soft beta radiation is means that category of radiation in which the energy is low enough that it will not penetrate any appreciable depth into animal tissue. In general, any radiation having an energy level below .2 mev. is considered a very soft beta radiation. Hard beta radiation has not been considered as a suitable source only because at thepresent time it is considered hazardous in that it will cause damage to the skin and the like.

The apparatus hereinbefore described can also be used for producting positive ions instead of negative ions merely by reversing the polarities on electrodes 24 and 44. i 1

It is apparent from the foregoing that We have provided an efficient method and apparatus which can be utilized in conjunction with a radiation source emitting soft beta particles to produce ions of the desired sign.

We claim:

1. In an ion generator adapted to be placed in an airstream, a radioactive source, means for mounting said radioactive source in said airstream, said last named means including means for shielding said radioactive source from said airstream to provide a zone of quiet air downstream from the radioactive source, means including said radioactive source serving as an electrode, an additional electrode mounted in said airstream, means for applying a charge of one sign to said radioactive source and for applying a charge of the opposite sign to said additional electrode whereby ions of the sign opposite the charge on the first named electrode, are col lected by the first named electrode and ions of the same sign as the charge of the first named electrode are repulsed therefrom and follow the electrostatic flux lines towards the additional electrode and pass into the airstream which sweeps them past the additional electrode and into the surrounding air.

2. Apparatus as in claim 1 wherein said radioactive source is tritium foil, said foil having good electrical conducting properties.

3. In an ion generator adapted to be placed in an air stream, a radioactive source of soft beta particles, the soft beta particles serving to create a dense plasma of ions of both signs in relatively close proximity to the radioactive source, means for mounting said radioactive source in the air stream, said means including means for shielding from the air stream the plasma of ions created by the soft beta particles, said radioactive source being formedof a conducting material and serving as an elec- 75.xepulsedtherefrom and follow the electrostatic; flux lines toward the additional electrode and pass into the air stream which sweeps them past the additional electrode and into the surrounding air.

4. In an ion generator adapted to be placed in an airstream, a radioactive source of soft beta particles, said radioactive source being in the form of a relatively flat member of conducting material lying in a plane at right angles to the path of flow of the airstream to form a zone of quiet air downstream from the member, the soft beta particles serving to create a dense plasma of ions of both signs in the zone of quiet air, said member serving as an electrode, an additional electrode disposed on the side of said member on which the dense plasma of ions of both signs are being created and being spaced from the dense plasma of ions, and means for applying a charge of one sign to said member and for applying a charge of the opposite sign to said additional electrode whereby the ions of the sign opposite the charge on the member are collected by the member and ions of the same sign as the charge of the member are repulsed therefrom and follow the electrostatic flux lines toward the additional electrode.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Ser. No. 376,930, Peycelon (A.P.C.), published May 25, 1943.

Production of Unipolar Air With Radium Isotopes, by T. L. Martin, Jr.; reprint from Electrical Engineering,

20 January 1954. 

